Field of the Invention
The present invention relates to an imaging apparatus that acquires an image signal and a method for controlling the imaging apparatus.
Description of the Related Art
Conventionally, when an electronic still camera or a video camera performs auto focus (referred to as “AF”) processing, a focus lens position where a high-frequency component of a luminance signal obtained by an image sensor including a charge-coupled device (CCD) is maximized is set as an in-focus position. One of such conventional methods is a scanning method. More specifically, the scanning method includes storing an evaluation value based on the high-frequency component of the luminance signal obtained by the image sensor (which can be referred to as “focus evaluation value”) for each focus lens position, while driving a focus lens in a predetermined focus detection range (e.g., the entire region).
The scanning method further includes setting an area (hereinafter, referred to as AF frame) to acquire the focus evaluation value at a central region of the screen or in the vicinity of an object detection area, acquiring a focus lens position corresponding to the maximum focus evaluation value (hereinafter, referred to as “peak position”) in each AF frame, and determining the in-focus position in a shooting operation.
The above-mentioned scanning method is usable not only to determine the in-focus position in a shooting operation but also to acquire a distance distribution in the screen by setting a plurality of AF frames for determination in image processing.
As discussed in Japanese Patent Application Laid-Open No. 2012-4716, it is conventionally known to divide the screen into some areas based on object distance information and perform predetermined image processing on each scene determined for each divided area.
However, in a case where the depth of field of a scene is deep, the division accuracy may deteriorate if two or more divided areas are present within the same depth of field even when the area division is performed based on a difference in the object distance. Further, in a case where a scene is so flat that there is not any distance difference, the area division may be erroneously performed due to a deviation in the distribution even though the area division cannot be actually performed based on the distance.
In the above-mentioned conventional technique discussed in the Japanese Patent Application Laid-Open No. 2012-4716, the distance division may be erroneously performed because checking the distance division accuracy in the screen is not performed.